The present invention concerns separators for three or two phase mixtures provided with an inlet centrifugal device for the separation from the fluid of the gas phase.
The separators of three or two phase mixtures, are used in the production of oil, and in particular for the separation of the different phases of crude oil which flow from producing wells as gas, oil, water and, if present, associated solid particles.
One separator for three phase mixtures, according to known technology, is illustrated in FIG. 1.
The separator essentially includes one horizontal vessel that, in order to facilitate the description of its operation, is considered divided in 5 different sections.
In the first section a preliminary separation and a reduction of the turbulence of the fluid entering from the inlet connection I is operated.
The separation is not complete because, due to fluid turbulence, part of the gas remains dispersed in the liquid phase while liquid droplets are carried over by the gas flow.
The liquid phases flow to the third section 3 through a stabilizing septum S, in order to evenly distribute the fluid, while the gas phase flows to the second section 2.
In the second section 2 the liquid droplets carried over are gradually separated from the gas and fall on the liquid phase that flows in the third section 3.
In order to obtain a correct separation by gravity, the gas flowing in the section 3 should maintain a reduced speed, along the separator, as necessary to guarantee the required separation efficiency.
However, before leaving the separator, the gas flows through a demister D that increases the final separation efficiency of the liquids carried over by the gas.
The third section 3 of the separator performs the gravity separation of the two liquid phases (water and oil).
In order to improve the liquid phase separation, the fluid can flow through a plate pack L, which has plates properly inclined and spaced, in order to reduce the operating time necessary for their separation by gravity.
The water, having a higher density than the oil, flows down toward the bottom, reaches the plate surface and is separated from the oil by coalescence effect.
The separated water flows, due to the inclination of the plates, towards the separator wall and reaches the bottom of the separator.
At the same time the oil, due to its lower density, flows in the opposite direction and is collected above the water level.
In the fourth section 4, located immediately after the plate pack, the separation of the water from the oil is completed.
The separated water is discharged from the bottom of the fourth section 4 through a vortex breaker 7 and a connection located in the bottom of the vessel, while the oil, which floats above the water surface, flows to the fifth section 5 overflowing a weir 6 utilized for this purpose.
From the fifth section 5 the oil is discharged passing through a vortex breaker and a connection 8 located in the bottom of the vessel.
A two phase separator, according to the prior art, is shown in FIG. 2.
Said two phase separator is realized by a cylindrical vertical vessel 10.
The gas and associated liquid enter the central zone of the separator through an inlet connection 11, while the separated gas leaves the separator through a connection 12 located in the top part of the vessel.
The separated liquid is discharged through a connection 13 after passing trough a vortex breaker located in the bottom of the separator vessel.
In the top of the two-phase separator 10, before the outlet connection 12, a demister D is utilized in order to improve the separation efficiency.
A disadvantage of said separators, operating according to known technology, is consequence of the considerable volume occupied by the gas, which is necessary for the separation of liquid droplets carried over by the gas which requires the utilization of vessels having considerable sizes.
An additional disadvantage of separators built according to the known technology is due to the turbulence of the entering fluid that requests a longer residence time of the liquids and consequently a larger volume to achieve the separation of the dispersed gas.
An additional disadvantage of the separators built according to the prior art is the lower total separation efficiency.
An additional disadvantage is due to the need to install a demister having a large volume as required for the separation of liquid particles from the gas. The purpose of the present invention is to provide three or two phase separators, utilizing a centrifugal device, for the separation of the gas phase from the fluid, said separators having a smaller size as compared to the size of separators according to the prior art which operate with a separation efficiency above 99% of liquid and solid particles, having a size of one micron or larger.
This and other results are reached using separators for three or two phase mixtures that are provided with a centrifugal device for the separation of the liquids from the gas which includes a centrifugal separation device (40, 70) placed at the inlet of the vessel (21, 64) for the separation of the gaseous phase from the incoming fluid stream characterized in that the aforesaid centrifugal separation device (40, 70) includes a first stage (40xe2x80x2, 70xe2x80x2) of annular section and an inner second stage (40xe2x80x3, 70xe2x80x3), coaxial to the fist one; said first stage being deliminated between the vessel internal wall (42, 63) and the external wall of the second stage that includes an element (47) built with a steel plate having a spiral shape around the vertical axis of the centrifugal separation device, in order to separate the gas from liquids directing the flow through a circular pattern that brings the liquid and solid droplets into contact with the internal wall of the vessel (42, 63) in the first stage and with the internal wall of the spiral element (47) of the second stage, thus separating (from the gas) said liquid and solid droplets, which eventually fall by gravity into the lower section of the centrifugal separator (20, 60). Additional characteristics of the separators provided in accordance with our invention are described herein. The separator for three or two phase mixtures in accordance with the invention are provided with one centrifugal separation device installed inside a vertical cylindrical vessel connected, for a three phase separator the gas phase from a mixed fluid (as, for example, the crude oil produced by one or more wells in an oil field).
The centrifugal separation device includes a first stage having a circular section delaminated by the internal surface of the vertical cylindrical vessel and by the external surface of the second stage and a second stage, internal and coaxial to the first one, provided by a spirally wrapped plate.
The two stages are associated to form a centrifugal device utilized to perform the separation of the gas from the liquids by imparting to the circulating fluid a circular path that brings the liquid in contact with the external surfaces of the first and second stage.
The characteristics and the advantages of a three or two phase centrifugal separator, in accordance with the present invention, will result more evident from the following description, that is exemplifies but does not restrict the invention.